Super absorbent polymer (SAP) is a synthetic polymer material having a function of absorbing water about 5 hundred times to about 1 thousand times of the weight of itself, and it has been differently named as super absorbency material (SAM), absorbent gel material (AGM), and so on by developing enterprises. The SAP disclosed above was started to be commercialized for sanitary items and is now being widely used to a water combination soil for horticulture, a water-stop material for civil engineering and construction, a nursery sheet, a freshness preservative in a food distribution field, a poultice material, and the like in addition to the sanitary fittings like a paper diaper for a child.
An inverse suspension polymerization method or an aqueous polymerization method is known as a method of preparing super absorbent polymer. For example, the inverse suspension polymerization is disclosed in Japanese Patent Publication Nos. Sho56-161408, Sho57-158209, Sho57-198714, and so on. As the aqueous polymerization method, a thermal polymerization method that polymerizes a polymer gel while fracturing and cooling the same in a kneader equipped with a spindle, and a photo-polymerization method that exposes a high-concentrated aqueous solution on a belt to UV rays and the like so as to carry out the polymerization and the dry at the same time are known.
Furthermore, the surface treatment of the resin powder obtained through the processes of polymerization, pulverization, drying, and final pulverization is being attempted for obtaining the hydrogel polymer having more excellent properties, or various modifications in the process are being attempted for improving the efficiency of polymerization, pulverization, and drying.
Meanwhile, the particle size, the absorbency, and the water holding property have been considered as important factors for evaluating the properties of the SAP, and many efforts have been made to improve the same. And, the concept of absorbing rate was introduced and the speed of absorption has been evaluated as the absorbing rate measured by using Vortex.
However, prior methods mentioned just the characteristics of each property, and did not mention the synergy effect when said properties are complexly combined. Furthermore, existing methods have mainly mentioned only the absorbing rate under non pressured condition of the SAP. Furthermore, they have not provided the SAP having rapid absorbing rate and good feelings of wearing at the same time until now.